Growth mode and asymptotic smoothing of sputtered Fe/Au multilayers studied by x-ray diffuse scattering

Abstract

The interfacial roughness of sputtered Fe[15 Å]/Au[21 Å] crystalline multilayers on MgO(001) was studied using x-ray specular and nonspecular reflectivity. The nonspecular scattering was collected using an image plate detector that allowed us to map the very weak x-ray diffuse intensity in one in-plane (Formula presented) and one out-of-plane (Formula presented) momentum-transfer direction. We have evaluated the interfacial static and dynamic roughness exponents from the in-plane diffuse scattering and the roughness conformality, and found them to be (Formula presented) and (Formula presented) respectively. From this result we show that the growth of this metallic thin film is described well by the Kardar-Parisi-Zhang (KPZ) model. By following the evolution of the interfacial roughness of this multilayer, starting from the MgO/Fe/Au heterostructure used to initiate a coherent lattice, we observe a tendency toward saturation in the growth and interfacial smoothing after the deposition of 40 bilayers. This asymptotic smoothing is induced by the mechanisms of the KPZ model and results in a reduction of the interfacial slope ρ as a function of time, according to (Formula presented) We have also found that the in-plane roughness cutoff length remains finite throughout the multilayer and does not increase to the lateral length of the sample, even after 100 bilayers have been grown. © 1997 The American Physical Society.